<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>边框</title>
    <style>
        /* 
        [边框]必须设置一下三个值:
        border-width: 5px;
        border-color: red;
        border-style: dashed;
        */
        .div1 {
            width: 200px;
            height: 200px;
            margin: 10px;
            color: white;
            background-color: blue;
            /* 三个值:上 左右 下 */
            border-width: 5px 200px 30px;
            border-color: red;
            border-style: solid;
        }

        .div2 {
            width: 200px;
            height: 200px;
            margin: 10px;
            color: white;
            background-color: blue;
            /* 四个值:上 右 下 左*/
            border-width: 5px 30px 60px 120px;
            border-color: red;
            border-style: solid;
        }

        .div3 {
            width: 200px;
            height: 200px;
            margin: 10px;
            color: white;
            background-color: blue;
            /* 两个值:上下 左右*/
            border-width: 60px 30px;
            border-color: red;
            border-style: solid;
        }
    </style>
</head>

<body>
    <div class="div1">[上] [左右] [下]</div>
    <div class="div2">[上] [右] [下] [左]</div>
    <div class="div3">[上下] [左右]</div>
</body>

</html>